Volume 2: Science
5. Diagnosis and therapy
Summary

5.51 To the present day, BSE is diagnosed from clinical observations confirmed by histopathological examination of the brain post-mortem. Histopathological diagnosis is time-consuming, requires the expertise of skilled pathologists and is expensive. Reliable immunological tests that can identify BSE in samples of cattle brain have recently been developed and are being applied in the UK to determine the incidence in over 30-month-old cattle going to slaughter, which is currently estimated as 0.5 per cent of those tested. In Switzerland the test is being used to guarantee that beef on the market is BSE-free. However, this test is insufficiently sensitive to be used ante-mortem on CSF or blood samples, and testing for pre-clinical disease in animals on their way to slaughter is not possible at the present time.

5.52 The diagnosis of vCJD likewise still depends on confirmation of clinical findings by histopathological examination of the brain post-mortem. Brain and tonsillar biopsies taken in the late stages of illness for the immunological detection of PrP^Sc can be diagnostic, but are less frequently used because of a high level of false negative results in the former and because both have a low level of acceptability by patients and their relatives. In any case, their use has been largely superseded by non-invasive MRI scanning, which reveals a positive 'pulvinar sign' in 78 per cent of affected patients. The availability of a reliable blood test would greatly aid clinical management but so far, no such test is available for clinical use.

5.53 With hindsight the early development of a test capable of detecting ruminant protein in animal feed would have had a dramatic effect on the size of the BSE epidemic. Such a test would have permitted the detection of cross-contamination in feed and the carry-over of existing stocks of cattle feed containing MBM after the introduction of the ruminant feed ban. An ELISA test for this purpose was eventually developed by 1994, but too late to have any real impact on the course of the epidemic.

5.54 A range of compounds have been investigated for their potential use in the treatment of TSEs, and some of these have shown a capacity to inhibit the production and accumulation of PrP^Sc. One compound, a synthetic -sheet breaker peptide, has been shown to reverse the conformation of PrP^Sc back to PrP^C and thus shows promise. However, none of these compounds has been assessed for its usefulness as an in vivo treatment for TSEs. The TSEs thus remain incurable and fatal diseases.